JP2747308B2 - Transmission power control method in wireless device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Table of Contents] Overview Industrial application field Conventional technology Problems to be solved by the invention Means for solving the problem (FIG. 1) Operation (FIG. 1) Embodiments (2 to 2) FIG. 6) Effect of the Invention [Overview] A method for controlling the transmission power on the transmission side in a wireless device of a wireless communication system using propagation in free space, wherein the transmission power is increased only when necessary to reduce unnecessary interference. With the aim of suppressing the occurrence and realizing effective use of radio waves, the transmitter on the transmitting side transmits information to which a check bit for code error correction is added via a wireless transmission path, and receives the information on the receiving side. If the reception level falls below the specified value or a code error occurs on the receiving side, the control information indicating that the transmission power should be increased is transmitted from the reception side to the transmission side, and the transmission side transmission power is reduced. While raising instantly, After the transmission power is increased, the transmission power is gradually reduced under required conditions.

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for controlling a transmission power on a transmission side in a wireless device of a wireless communication system using propagation in free space.

Generally, in a wireless communication system using propagation in free space, there is always a possibility that its own wireless communication state is deteriorated due to fading that occurs in the space and interference from other wireless communication systems. doing. For this reason, it is desired to deal with fading without causing interference.

[Prior Art] Conventionally, in a wireless communication system, the power (transmission power) of a transmission radio wave from a transmission side is constantly reduced in order to remedy a decrease in a reception level on a receiving side due to fading generated in a wireless transmission path. To be high. The transmission power at this time is usually set to be several tens of dBm higher than the transmission power required when no fading occurs, in consideration of a fading margin.

[Problems to be Solved by the Invention] By the way, in general, although the probability that a radio channel is disconnected due to fading is on the order of thousands to tens of thousands, each radio communication system has Since all systems are operated with the transmission power always high in anticipation of the fading margin, the effects of interference will inevitably occur between each system, leading to deterioration of the wireless communication condition and impeding the effective use of radio waves. It is a factor.

If all wireless communication systems have the function of automatic power control (APC), when necessary (reduction of reception level, etc.)
If only the transmission power on the transmission side is controlled to be increased, the operation of the wireless device which is many times as large as the wireless communication device currently in operation can be performed without causing unnecessary mutual interference.

The present invention seeks to solve such a problem, by increasing the transmission power only when necessary,
Suppressing unnecessary interference and realizing effective use of radio waves,
An object of the present invention is to provide a transmission power control method in a wireless device.

[Means for Solving the Problems] FIG. 1 is an explanatory view of the principle of the present invention.

The present invention relates to a method for controlling transmission power when transmitting information to which a check bit for correcting a code error is added from a transmitter on the transmission side via a wireless transmission path and receiving the information at the receiver on the reception side. It is.

In FIG. 1, S1 is a step for determining whether or not the reception level is below a specified value on the receiving side, and S2 is where a code error has occurred on the receiving side based on a correction operation using a check bit for correcting a code error. Step of determining whether or not, S3 is a step of transmitting a control command to increase the transmission power from the receiving side to the transmitting side when it is determined Yes in these steps S1, S2, S4 is from the receiving side When the transmission power increase control command is received, the transmission power is instantaneously increased, and in step S5, the reception level is maintained for a certain period of time without any condition (steps S1 and S2) for increasing the transmission power after the transmission power is increased. Step of determining whether or not, S6 is a step of transmitting a control command to reduce the transmission power from the receiving side to the transmitting side when it is determined Yes in step S5, S7 is From Shin side is gradually reduced step the transmission power when receiving the transmission power lowering control command.

[Operation] With the above-described configuration, in the transmission power control method of the present invention, in steps S1 and S2, when it is determined that the reception level has fallen below the specified value on the reception side or that a code error has occurred on the reception side. In step S3, a control command to increase the transmission power is transmitted from the reception side to the transmission side. When the transmission side receives the transmission power increase control command from the reception side, the transmission power is instantaneously increased (step S4).

On the other hand, after the increase in the transmission power, the receiving side determines whether or not the stable state of the reception level has been maintained for a certain period of time or longer without generating the transmission power increase condition corresponding to steps S1 and S2 in step S5. When the condition of step S5 is satisfied, in step S6,
A control command to reduce the transmission power is transmitted from the receiving side to the transmitting side. When the transmission side receives the transmission power decrease control command from the reception side, the transmission power is gradually decreased (step S7).

[Examples] Hereinafter, the present invention and examples will be described with reference to the drawings.

FIG. 2 is a block diagram showing an example of a wireless communication system to which the transmission power control method as one embodiment of the present invention is applied. In FIG. The receiving side, 4 is a modulator (MOD) of the transmitting side 1, and 5 is a transmitter of the transmitting side 1. The transmitter 5 converts an intermediate frequency (IF) signal from the modulator 4 into a high frequency (microwave) signal. Up-converter 5a, a variable attenuator 5b capable of attenuating and adjusting the amplitude of the high-frequency signal from the up-converter 5a to control the transmission power, and amplifying the signal from the variable attenuator 5b and transmitting the amplified signal from the transmitting antenna 6. High-frequency amplifier 5c and a detector 5d that can detect the transmission power
It is composed of

Here, information transmitted from the transmitter 5 of the transmission side 1 to the reception side 3 via the wireless transmission path 2 includes code error correction (FE
C; Forward Error Correct) check bit is added.

7a is a main antenna on the receiving side, 7b is a sub-antenna on the receiving side, 8 is a receiver on the receiving side 3, and this receiver 8
Are down-converters 8a, 8b connected to the antennas 7a, 7b, respectively, for receiving weak high-frequency signals and converting them into IF signals.
And phase shifters 8c and 8d connected to the down converters 8a and 8b to change the amount of transmission phase, a hybrid combiner 8e that combines the signals from the phase shifters 8c and 8d, and amplifies the signal from the combiner 8e. Variable gain amplifier 8f and down converters 8a and 8b
And a reception level detection unit 8g for detecting the reception level of the reception radio wave in the communication device.

In the receiver 8, a system including the sub-antenna 7b, the down-converter 8b, and the phase shifter 8d is provided for combined space diversity.

Further, 9 is a demodulator (DEM) for demodulating a signal from the receiver 8, and 10 is a receiving code processing unit (10) for receiving a demodulated signal from the demodulator 9 and performing a correction operation by a check bit when a code error occurs. RCC). When the error correction operation is performed, the reception code processing unit 10 determines that a code error has occurred, and sends a High level signal to a determination circuit 11c described later.

On the other hand, reference numeral 11 denotes a receiving-side control unit. The control unit 11 sets a specified value (threshold value; for example, about -40 dBm) for the reception level by a specified value setting unit 11a and a specified value setting unit 11a. Comparator 11b that compares the specified value with the actual reception level from reception level detector 8g.
And a determination circuit 11c and a parallel / serial (P
/ S) converter 11d.

Here, the judgment circuit 11c receives the comparison result from the comparator 11b, and when the actual reception level falls below the specified value, when a code error occurs (the signal from the reception code processing unit 10
When the level changes from the low level to the high level), or when an error (malfunction or open loop occurs) occurs in the control system (not shown) upon receiving the control line status signal,
It outputs a control command to increase the transmission power. Further, when the determination circuit 11c determines that the stable state of the reception level is maintained for a certain period of time or more without the occurrence of the transmission power increase condition, that is, the above-described condition (1) after the output of the transmission power increase control command, , Which outputs a control command to lower the transmission power.

The parallel / serial converter 11d converts a signal such as a control command output in parallel from the determination circuit into a serial signal and transmits the signal to the transmitting side 1 via the digital service channel 12.

Further, 13 is a transmission side control unit, and this control unit 13
A serial / parallel (S / P) converter 13a for converting a serial signal transmitted via the digital service channel 12 into a parallel signal, a control unit 13b described later, and a maximum transmission level of transmission power from the transmitter 5. (For example, about 30 dBm) and setting units 13c and 13d for setting a minimum transmission level (for example, about 20 dBm).

When receiving the transmission power increase control command from the receiving side 3 as a rising signal from the low level to the high level, the control unit 13b instantaneously increases the transmission power to the maximum set value set by the maximum transmission level setting unit 13c. Then, a control signal is output to the variable attenuator 5b of the transmitter 5 to control the holding at the maximum set value. Further, the control unit 13b changes the transmission power decrease control command from the receiving side 3 from the high level to the low level.
When received as a falling signal to the w level, a control signal is output to the variable attenuator 5b of the transmitter 5 so as to gradually lower the transmission power to the minimum setting value set by the minimum transmission level setting unit 13d. .

As a circuit for controlling the attenuator 5b in this manner, for example, an integrator 14 having a different time constant between charge and discharge as shown in FIG. 3 is used. In FIG. 3, 15a is a rectifier in the charging direction, 15b is a rectifier in the discharging direction,
16a is a resistor during charging (resistance value R ₁ ), 16b is a resistor during discharging (resistance value R ₂ ), and 17 is a capacitor (capacitance C). In such a circuit, by appropriately setting the time constant T ₁ = R ₁ · C at the time of charging and the time constant T ₂ = R ₂ · C at the time of discharging, as shown in FIG. The transmission power level can be adjusted. For example, when the transmission power increase control command (L → H) is received, the transmission power is instantaneously increased from the minimum set value to the maximum set value at about 100 dB / sec, while the transmission power decrease control instruction (H → L) is received. And transmission power from maximum setting to minimum setting 10dB / 5mi
It can be lowered gradually by about n.

The interface of the control units 11 and 13 is LS-TTL Lev
When the control unit 11 or 13 is disconnected, the interface condition is considered fail-safe so that the transmission power from the transmitter 5 is maintained on the maximum set value side.

The control of the transmission power is performed as shown in FIG. 5 by the wireless communication system configured as described above.

Normally, the transmission power from the transmitter 5 on the transmission side 1 is set to the minimum setting value (for example, 20 dBm) set by the minimum transmission level setting unit 13d by the control unit 13b based on the feedback signal from the detector 5d. The holding is controlled.

Then, in the determination circuit 11c of the receiving side 3, when it is determined that an abnormality has occurred in the control line (step A1), when it is determined that the reception level has fallen below the specified value (step A1).
A2) Alternatively, if it is determined that a code error has occurred on the receiving side 3 (step A3), the determination circuit 11 of the receiving side 3
From c, a transmission power increase control command is transmitted to the transmission control unit 13 via the parallel / serial converter 11d and the service digital channel 12 (step A4).

Here, the control line abnormal state determined in step A1 occurs due to a failure, fade-out, power cutoff, or the like of a device such as the control unit 11 or 13, and the state determined in step A2 includes a space loss. The state determined in step A3 due to the large fading and the state determined in step A3 is due to frequency characteristic deterioration due to fading, interference with other systems, deterioration due to up-fading, and the like.

Further, the determination of the decrease in the reception level in step A2
The reception level detected by the reception level detection unit 8g is compared with a specified value preset by the specified value setting unit 11g.
The comparison is performed in 1b, and when the reception level becomes lower than the specified value, the judgment circuit 11c receives the High level signal output from the comparator 11b and performs the operation.

Further, the determination of the occurrence of a code error in step A3 includes:
It is performed as follows. For example, when a BCH code is used, the syndrome calculation results are all “0 (Low)” if there is no code error, but all “0 (Low)” if there is a code error.
(Low) ", and the OR of the result of the syndrome calculation indicates that an error has occurred. In this manner, when a code error occurs, the high-level signal is output from the reception code processing unit 10. Output to the judgment circuit 11c,
Determines that a code error has occurred.

Now, in the transmitting side control unit 13 which has received the transmission power increase control command from the receiving side 3, the control unit 13b is converted by the control command serial / parallel converter 13a and receives the control command.
Outputs a control signal to the variable attenuator 5b, and raises the transmission power instantaneously (for example, about 100 dB / sec) from the minimum setting value to the maximum value (for example, about 30 dBm) set by the maximum transmission level setting unit 13c. (Step A
Five).

In this way, when the reception level becomes lower than the specified value, or when a code error starts to occur and it is predicted that the error will continue to continue after the current state is maintained, furthermore, if the control line is disconnected, etc. When an unexpected situation occurs, the transmission power is instantaneously increased so that the reception side 3 can obtain a high-speed response, thereby preventing the wireless communication state from deteriorating.

For example, if the output condition of the transmission power increase control command is a decrease in the reception level determined in step A2,
As shown in FIG. 6, the reception level at the receiving side 3 is obtained from the spatial loss when the transmission power is at the minimum setting value—the spatial loss when the transmission power is at the maximum setting value—from the reception level characteristic curve A. The transition to the reception level characteristic curve B almost instantaneously. Therefore, the reception level should be a sufficiently specified value (for example, -30 dB) even if the spatial loss is further increased.
m), it is possible to prevent the wireless communication state from deteriorating.

As described above, after the transmission power is controlled to increase to the maximum setting value, the transmission power is set by the control unit 13b by the maximum transmission level setting unit 13c based on the feedback signal from the detector 5d. It is held and controlled to the maximum set value (for example, 30 dBm).

Then, in the determination circuit 11c of the receiving side 3, the steps A1 to A
Without the transmission power increase condition corresponding to 3,
When it is determined that the stable state of the reception level for a predetermined time or more is maintained (step A6), the determination circuit of the reception side 3
From 11c, the transmission power lowering control command is transmitted to the transmission side control unit 13 via the parallel / serial converter 11d and the service digital channel 12 (step A7).

In the transmitting side control unit 13 which has received the transmission power decrease control command from the receiving side 3, the control command is transmitted to the serial / parallel converter 13
The control unit 13b, which has been converted at a and receives the control command, outputs a control signal to the variable attenuator 5b, and the transmission power, from the maximum setting value to the minimum value set by the minimum transmission level setting unit 13d, Gradually (for example, about 10dB / 5min)
Lower (Step A8).

By gradually lowering the transmission power in this manner, it is possible to monitor again whether or not the transmission power increase condition corresponding to steps A1 to A3 occurs with the decrease in the transmission power.

As described above, according to the transmission power control method of the present embodiment, the transmission power is normally held at the minimum set value to prevent the occurrence of interference. However, when the reception level becomes lower than the specified value, a code error occurs. The transmission power is automatically and instantaneously controlled to rise to the maximum set value only when either of the following conditions occurs or when an unexpected situation such as control line disconnection occurs, fading. In addition to being able to prevent the reception level from rising with sufficient follow-up to prevent deterioration of the radio passage condition, the transmission power can be increased only when necessary, so that multiple wireless communications can be performed without causing unnecessary mutual interference. The system can be operated, and effective use of radio waves can be realized.

After the transmission power rises, the required conditions (step
Since the transmission power is gradually reduced in A6), it is possible to monitor whether the transmission power increase condition occurs again due to the decrease in the transmission power, and to maintain the transmission power to the minimum set value while maintaining the quality of the wireless communication state. Can be lowered.

Further, according to the system of the present embodiment, the existing equipment only needs to be additionally equipped with the control units 11 and 13 as shown in FIG.
It can be realized with low cost, high reliability and good operability.

In the above-described embodiment, an alarm unit that generates an alarm when a transmission power increase condition corresponding to steps A1 to A3 occurs may be provided.

In the above embodiment, the case where the present invention is applied to one channel of the wireless communication line is described. However, by providing the control units 11 and 13 shown in FIG. 2 in parallel for each channel, The transmission power can be controlled for each channel.

Further, when a plurality of channels are provided, as means for controlling the increase of the transmission power, there are means for controlling the transmission power for each channel and means for simultaneously controlling all the channels.
In the former method, since the interference condition between the channels changes with the transmission power control, the IRF (Interfeature) between the channels is changed.
It is necessary to ensure a sufficient rence rejection factor) and sufficient antenna V / H interference. However, this method is efficient without outputting unnecessary transmission power. On the other hand, in the latter means, unnecessary transmission power is output, but it is sufficient to consider certain interference conditions, and the security is high.

[Effects of the Invention] As described above in detail, according to the transmission power control method in the wireless device of the present invention, only when the reception level falls below a specified value or a code error occurs on the reception side, the transmission side Since the transmission power is increased instantaneously, the reception level can be increased with sufficient followability against fading and the like, and the deterioration of the wireless communication state can be prevented, and the transmission power is increased only when necessary. Unnecessary mutual interference does not occur, a large number of wireless communication systems can be operated simultaneously, and there is an effect that effective use of radio waves can be realized. In addition, since the transmission power can be gradually reduced under the required conditions after the transmission power rises, it is possible to monitor whether the transmission power increase condition occurs again with the decrease in the transmission power, and to maintain the transmission power while maintaining the quality of the wireless communication state. There is also an effect that the descending control can be performed.

[Brief description of the drawings]

FIG. 1 is a diagram illustrating the principle of the present invention, FIG. 2 is a block diagram showing an example of a wireless communication system to which a transmission power control method according to an embodiment of the present invention is applied, and FIG. FIG. 4 is a circuit diagram showing an example of a variable attenuator control circuit in an example. FIG. 4 is a time chart for explaining the operation of the variable attenuator control circuit shown in FIG. 3. FIG. 5 is a transmission diagram according to an embodiment of the present invention. FIG. 6 is a graph for explaining the effect of one embodiment of the present invention. In the figure, 1 is a transmitting side, 2 is a wireless transmission path, 3 is a receiving side, 4 is a modulator, 5 is a transmitter, 5a is an up-converter, 5b is an attenuator, 5c is a high-frequency amplifier, 5d is a detector, and 6 is a detector. 7a is the receiving main antenna, 7b is the receiving sub-antenna, 8 is the receiver, 8a and 8b are downconverters, 8c and 8d are phase shifters, 8e is a hybrid combiner, and 8f is a variable gain amplifier. , 9 is a demodulator, 10 is a reception code processing section, 11 is a reception side control section, 11a is a prescribed value setting section, 11b is a comparator, 11c is a decision circuit, 11d is a parallel / serial converter, and 12 is a digital service channel. , 13 is a transmission side control unit, 13a is a serial / parallel converter, 13b is a control unit, 13c is a maximum transmission level setting unit, 13d is a maximum transmission level setting unit, 14 is an integrator, 15a and 15b are rectifiers, 16a, 16b is a resistor, and 17 is a capacitor.

Claims (1)

(57) [Claims] A transmitter (5) of a transmitting side (1) transmits information to which a check bit for correcting a code error is added via a wireless transmission path (2), and transmits the information to a receiving side (3). When the receiving level is below the specified value or a code error occurs at the receiving side (3) when the receiving side (8) receives the control information, the control information indicating that the transmission power should be increased is received at the receiving side (3). 3) The transmission power is transmitted from the transmission side (1) to the transmission side (1), and while the transmission power of the transmission side (1) is instantaneously increased, the transmission power is gradually reduced under required conditions after the transmission power is increased. A transmission power control method in a wireless device, characterized by: